The present invention relates to a new and improved construction of apparatus for applying preparation agents onto a bundle of filaments which is of the type comprising an applicator head with a slit for applying the preparation agent and a guide edge for guiding the filament bundle and a supply duct for supplying the preparation agent to the slit. Such devices are used mainly in the textile industry for coating an endless filament.
The purpose of a preparating device is to apply the preparation agents at an even supply rate to the filament bundle and to transfer it evenly distributed to the filament bundle. Devices for applying preparation agents to filament bundles are known as such.
One such type of device consists, for instance, of an applicator head containing a reservoir for the preparation agent. In this arrangement there is provided at a guide surface formed by the upper wall of the reservoir and thus extending upwardly a slit which extends over the width of the guide surface. The slit serves for applying the preparation agents to a filament bundle guided in substantially horizontal direction across the guide surface. The applicator is provided with a preparation agent-supply device at its lower portion. The preparation agent, in this arrangement, is applied from the reservoir to the filament bundle with a very low pressure approaching zero.
The disadvantage of such type device is seen in the imprecision of the applied quantities of preparation agent due to the practically direct connection between the preparation agent reservoir and the filament guiding surface. In this arrangement no buffer zone exists between the preparation agent reserve or supply and the filament bundle, so that even the smallest pressure variations in the preparation agent supply directly act upon the preparation agent application.
Due to the necessarily horizontal arrangement of the filament bundle on the guide surface a further disadvantage is that at high thread or filament speeds of, for instance, in excess of 2,000 meters per minute, a high hydrodynamic friction between the wetted filament bundle and the guide surface is generated in such manner that there can be caused undesirable additional thread tension at the thread winding position.
Furthermore, the horizontal guide arrangement in a substantially vertical thread path necessitates two thread deflections which is technically and economically complicated and thus constitutes a disadvantage.
Also known are nozzles of round cross-section made of ceramic material provided with a fine bore in axial direction for supplying the preparation agent and with a wedge-shaped slit coinciding with the bore for guiding the filament bundle. The bore in this arrangement merges into the slit at the narrowed part of the wedge which guides the thread.
The disadvantage of a nozzle of such type resides in the fact that the thread is too narrowly bundled at the preparation agent application point in such manner that there is not insured for any even distribution of the preparation agent across the whole cross-section of the filament bundle.